The present invention relates to a method and device for increasing the shelf life of oxygen sensitive products such as ground beef and other meat. More particularly, the invention relates to an improved stopper for attachment to the hopper of a stuffer used in the packaging of such oxygen sensitive food products. The stopper has means for purging the ambient air surrounding the product during the stuffing operation and means for disassembling and cleaning the stopper between periods of use.
As the global demand for processed meat increases, processors continue to demand equipment, supplies, and raw material to enhance their ability to increase productivity, profits, customer satisfaction, and most importantly sanitation measures. One high-speed packaging system for ground meat is a combination of a stuffer with a high-speed chub packaging machine. In this system, the meat, such as beef, is coarsely ground, i.e., about 9.5 mm to 19.0 mm diameter die cut, and dumped or otherwise conveyed into a hopper of the stuffer or a stuffing pump; see U.S. Pat. No. 4,417,434 and 5,830,050, respectively. The coarsely ground meat is then conveyed to the chub packaging machine; see U.S. Pat. Nos. 4,085,778; 4,085,779; and 4,939,885. An example of a commercially available high-speed chub packaging machine is a 4000 series KartridgPak chub packager. The chub packager packages the meat, with or without added an inert gas, e.g., carbon dioxide, into oxygen-impermeable casings; see U.S. Pat. No. 4,707,444.
The chubs usually range from about 4.5 kg to 9.0 kg and have a fat content ranging from about 7% to 30%. The chubs are then shipped and stored under refrigeration until needed. In the case of ground beef, they may be distributed to supermarkets that regrind the ground beef from the chubs and repackage them in Styrofoam trays, which are over wrapped with a clear plastic film for sale to the consumer. The shelf life of the repackaged product is relatively short. This is primarily due to the prolonged exposure of the meat product to the residual oxygen present in the entire packaging system. It is well known that the prolonged exposure of the meat product to oxygen also bacterial decay and discoloration of the meat.
It is known to use a modified atmosphere environment whereby a preservation-enhancing gas mixture, typically containing a bacterial inhibitor such as carbon dioxide, is introduced into the casing during the chub packaging operation. This method has led to increases in the maximum shelf life of the product of about twenty days.
It would be desirable to be able extend the shelf life of the packaged meat within chubs beyond the present maximum shelf life of about twenty days, and preferably, up to a maximum shelf life of sixty or even ninety days.
One type of commercially available stuffer, e.g., Henry and Sons"" AC-20 Continuous Vacuum Stuffer; set Appendix I taken from a web site of Henry and Sons for specifications and other details, which information is incorporated herein by reference. The stuffer comprises a funnel-shaped hopper, a scraper for keeping the ground meat from sticking to the inside of the hopper and a stopper attached to the top of the hopper. The scraper is attached to a ring gear connected to a drive mechanism. The ring gear is located in the bottom of the hopper adjacent the outlet and has either a right or a left spiral. The ring gear causes the scraper to rotate usually in a counterclockwise direction. The combination of the scraper and ring gear forces the ground meat in a downward spiral manner toward the hopper outlet and the mechanism that feeds the ground meat to the chub packaging machine. In the commercially available continuous vacuum stuffers, the hopper, ring gear, and stopper are stainless steel and the scraper is an industrial plastic, such as nylon.
The stopper is usually constructed of hollow tubing, closed at each end, and protrudes down into the bottom of the hopper adjacent, but not touching, the ring gear. The stopper stops, or at less slows down, the meat from continuing to spin or rotate around the lower portion of the hopper and allows the scrapper and ring rear combination to function more efficiently to force the meat out through the stuffer outlet and into the conveyer to the chub packager. A commercially available stopper consists of a straight rod extending along the longitudinal axis of the hopper and has extensions, called a paddle, attached to the lower end of the rod that is angled at least 15 degrees from vertical. The stopper also includes attachment means for fixedly attaching the stopper to the hopper.
The device and method of the present invention dramatically increases the shelf life of oxygen sensitive food products by introducing an inert gas during the stuffing stage of the packaging process.
The present invention comprises an improvement in the stuffer in which the stopper has means for injecting an inert gas or blend of inert gases into the food product as it is being pushed toward the stuffer outlet. By introducing the inert gas at this early stage in the chub packaging operation, the oxygen content within each chub is reduced from about 7% using the prior art method to 0.5% and less using the present invention. Without being bound by the theory of the mechanism, it is believed that inert gas forces substantially all of the ambient air away from the entire surface area of the product as it is being circulated in the lower portion of the stuffer hopper and prior to being forced out through the stuffer outlet.
Preferably, the inert gas or blend of gases is heavier than air. Therefore, the inert gas injected from the stopper displaces the ambient air surrounding the meat entering the hopper and purges the air away from the meat. The remaining oxygen present in the stuffer outlet and conveyor to the chub packager has been found to be dramatically reduced from the current operation of adding an inert gas down flow from the stuffer.
As discussed in further detail in the Examples section below, measurements of the oxygen content in the chubs leaving the packaging machine has been found to be in the range of about 0.2 to 0.5 volume % oxygen using the device of the present invention. The resulting shelf life of the ground meat has been found to increase to about 90 days using the apparatus and method of the present invention.
In contrast, introducing an inert gas into the casing as the chubs are being formed in the chub packager results in reducing the ambient oxygen level from 21% to only about 7-volume %. The resulting shelf life of the ground meat has been found to be about 21 days using the apparatus and method of the prior art.
Various means can be used injecting or otherwise introducing the inert gas during the stuffing operation. One injection means is to place a mesh screen in the hollow stopper connected to a source of inert gas where the mesh size of the screen is designed to avoid becoming plugged with the product. Another injection means is to place the plurality of orifices along the lower section of the stopper connected to the inert gas source. Preferably, nozzles are placed in the orifices to avoid clogging them with product. Another injection means is to place either the orifices or the nozzles in the paddle adjacent to the lower end of the stopper.
A still further injection means is to construct the hollow stopper connected to an inert gas supply in at least two sections; (1) the upper section connects to the support at the top of the hopper; and (2) the bottom section having the plurality of holes. A suitable coupling joins the two sections. The coupling permits the lower section to be easily detached from the upper section for cleaning and sanitation procedures. A further modification of this injection means is to add a vertical section that is coupled to the upper section and fixedly attach to the bottom section that includes a paddle.